Most prior internal combustion, such as a four-stroke piston engines, use an opening cam to open the valve, but use heavy spring(s) to close the valve. Though there are many detailed variations to how prior systems are implemented, the cam and valve are generally either linked directly whereby the cam presses directly on the valve or via rocker arms where the cam is generally not situated directly over the valve.
Disadvantages of the heavy spring system are: i) heavy spring loading creates more work for the engine thus robbing horsepower, ii) valves are able to “float” (i.e., not follow the valve profile closely) at high RPM, and iii) if the cam is situated directly over the valve, the heavy spring system generally requires removal of the camshaft for valve adjustment.
Since 1956, Ducati Motorcycles have used opening and closing cams with separately articulating rocker arms to indirectly link the cams to the poppet valve in an offset fashion. In the Ducati system, the cam is not situated directly over the valve and thus the cam is not collinear with the valve stem. The Ducati system also requires a spring (relatively small compared to conventional internal combustion, piston engines) to do final valve closing/sealing. The Ducati spring is actuated through the entire valve travel. Disadvantages of the Ducati system include: i) more reciprocating mass created by the rocker arms, ii) complex valve adjustment procedures relative to the present invention, and iii) a spring (rotary, or torsion) used for final valve closing/sealing increases force proportionately with valve travel.
The embodiments of the present invention pertain to a poppet valve actuation system for internal combustion engines that uses a cam to open the valve and a cam to close the valve with cam followers linked directly with a tension member and without additional articulating members, commonly known as rocker arms. The size and proportions of the system and its components can be altered to fit various applications. This invention was developed for internal combustion engines but can be applied to any system requiring controlled, cam-driven reciprocation of an element.